Firstly, I admire your honesty with your wife. It will take her a long time to trust you again, but it's best for everyone.
As far as this other woman, you can buy cheap security devices, or even set up a camera to catch anything going on while you're away or sleeping. Legally, you can't do anything about her unless you have documented incidents (video, police reports, etc.) I can't tell you anything about her personality, but if you have any gut feelings, I'd follow them. Good luck!